/*
 * Copyright 2002-2023 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jdbc.datasource;

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;

import javax.sql.DataSource;

import com.kfyty.loveqq.framework.core.autoconfig.InitializingBean;
import org.springframework.lang.Nullable;
import org.springframework.transaction.CannotCreateTransactionException;
import org.springframework.transaction.TransactionDefinition;
import org.springframework.transaction.TransactionSystemException;
import org.springframework.transaction.support.AbstractPlatformTransactionManager;
import org.springframework.transaction.support.DefaultTransactionStatus;
import org.springframework.transaction.support.ResourceTransactionManager;
import org.springframework.transaction.support.TransactionSynchronizationManager;
import org.springframework.transaction.support.TransactionSynchronizationUtils;
import org.springframework.util.Assert;

/**
 * {@link org.springframework.transaction.PlatformTransactionManager} implementation
 * for a single JDBC {@link javax.sql.DataSource}. This class is capable of working
 * in any environment with any JDBC driver, as long as the setup uses a
 * {@code javax.sql.DataSource} as its {@code Connection} factory mechanism.
 * Binds a JDBC {@code Connection} from the specified {@code DataSource} to the
 * current thread, potentially allowing for one thread-bound {@code Connection}
 * per {@code DataSource}.
 *
 * <p><b>Note: The {@code DataSource} that this transaction manager operates on
 * needs to return independent {@code Connection}s.</b> The {@code Connection}s
 * typically come from a connection pool but the {@code DataSource} must not return
 * specifically scoped or constrained {@code Connection}s. This transaction manager
 * will associate {@code Connection}s with thread-bound transactions, according
 * to the specified propagation behavior. It assumes that a separate, independent
 * {@code Connection} can be obtained even during an ongoing transaction.
 *
 * <p>Application code is required to retrieve the JDBC {@code Connection} via
 * {@link DataSourceUtils#getConnection(DataSource)} instead of a standard
 * EE-style {@link DataSource#getConnection()} call. Spring classes such as
 * {@link org.springframework.jdbc.core.JdbcTemplate} use this strategy implicitly.
 * If not used in combination with this transaction manager, the
 * {@link DataSourceUtils} lookup strategy behaves exactly like the native
 * {@code DataSource} lookup; it can thus be used in a portable fashion.
 *
 * <p>Alternatively, you can allow application code to work with the standard
 * EE-style lookup pattern {@link DataSource#getConnection()}, for example
 * for legacy code that is not aware of Spring at all. In that case, define a
 * {@link TransactionAwareDataSourceProxy} for your target {@code DataSource},
 * and pass that proxy {@code DataSource} to your DAOs which will automatically
 * participate in Spring-managed transactions when accessing it.
 *
 * <p>Supports custom isolation levels, and timeouts which get applied as
 * appropriate JDBC statement timeouts. To support the latter, application code
 * must either use {@link org.springframework.jdbc.core.JdbcTemplate}, call
 * {@link DataSourceUtils#applyTransactionTimeout} for each created JDBC
 * {@code Statement}, or go through a {@link TransactionAwareDataSourceProxy}
 * which will create timeout-aware JDBC {@code Connection}s and {@code Statement}s
 * automatically.
 *
 * <p>Consider defining a {@link LazyConnectionDataSourceProxy} for your target
 * {@code DataSource}, pointing both this transaction manager and your DAOs to it.
 * This will lead to optimized handling of "empty" transactions, i.e. of transactions
 * without any JDBC statements executed. A {@code LazyConnectionDataSourceProxy} will
 * not fetch an actual JDBC {@code Connection} from the target {@code DataSource}
 * until a {@code Statement} gets executed, lazily applying the specified transaction
 * settings to the target {@code Connection}.
 *
 * <p>This transaction manager supports nested transactions via the JDBC 3.0
 * {@link java.sql.Savepoint} mechanism. The
 * {@link #setNestedTransactionAllowed "nestedTransactionAllowed"} flag defaults
 * to "true", since nested transactions will work without restrictions on JDBC
 * drivers that support savepoints (such as the Oracle JDBC driver).
 *
 * <p>This transaction manager can be used as a replacement for the
 * {@link org.springframework.transaction.jta.JtaTransactionManager} in the single
 * resource case, as it does not require a container that supports JTA, typically
 * in combination with a locally defined JDBC {@code DataSource} (e.g. a Hikari
 * connection pool). Switching between this local strategy and a JTA environment
 * is just a matter of configuration!
 *
 * <p>As of 4.3.4, this transaction manager triggers flush callbacks on registered
 * transaction synchronizations (if synchronization is generally active), assuming
 * resources operating on the underlying JDBC {@code Connection}. This allows for
 * setup analogous to {@code JtaTransactionManager}, in particular with respect to
 * lazily registered ORM resources (e.g. a Hibernate {@code Session}).
 *
 * <p><b>NOTE: As of 5.3, {@link org.springframework.jdbc.support.JdbcTransactionManager}
 * is available as an extended subclass which includes commit/rollback exception
 * translation, aligned with {@link org.springframework.jdbc.core.JdbcTemplate}.</b>
 *
 * @author Juergen Hoeller
 * @see #setNestedTransactionAllowed
 * @see java.sql.Savepoint
 * @see DataSourceUtils#getConnection(javax.sql.DataSource)
 * @see DataSourceUtils#applyTransactionTimeout
 * @see DataSourceUtils#releaseConnection
 * @see TransactionAwareDataSourceProxy
 * @see LazyConnectionDataSourceProxy
 * @see org.springframework.jdbc.core.JdbcTemplate
 * @see org.springframework.jdbc.support.JdbcTransactionManager
 * @since 02.05.2003
 */
public class DataSourceTransactionManager extends AbstractPlatformTransactionManager implements ResourceTransactionManager, InitializingBean {
    @Nullable
    private DataSource dataSource;

    private boolean enforceReadOnly = false;


    /**
     * Create a new {@code DataSourceTransactionManager} instance.
     * A {@code DataSource} has to be set to be able to use it.
     *
     * @see #setDataSource
     */
    public DataSourceTransactionManager() {
        setNestedTransactionAllowed(true);
    }

    /**
     * Create a new {@code DataSourceTransactionManager} instance.
     *
     * @param dataSource the JDBC DataSource to manage transactions for
     */
    public DataSourceTransactionManager(DataSource dataSource) {
        this();
        setDataSource(dataSource);
        afterPropertiesSet();
    }


    /**
     * Set the JDBC {@code DataSource} that this instance should manage transactions for.
     * <p>This will typically be a locally defined {@code DataSource}, for example a
     * Hikari connection pool. Alternatively, you can also manage transactions for a
     * non-XA {@code DataSource} fetched from JNDI. For an XA {@code DataSource},
     * use {@link org.springframework.transaction.jta.JtaTransactionManager} instead.
     * <p>The {@code DataSource} specified here should be the target {@code DataSource}
     * to manage transactions for, not a {@link TransactionAwareDataSourceProxy}.
     * Only data access code may work with {@code TransactionAwareDataSourceProxy} while
     * the transaction manager needs to work on the underlying target {@code DataSource}.
     * If there is nevertheless a {@code TransactionAwareDataSourceProxy} passed in,
     * it will be unwrapped to extract its target {@code DataSource}.
     * <p><b>The {@code DataSource} passed in here needs to return independent
     * {@code Connection}s.</b> The {@code Connection}s typically come from a
     * connection pool but the {@code DataSource} must not return specifically
     * scoped or constrained {@code Connection}s, just possibly lazily fetched.
     *
     * @see LazyConnectionDataSourceProxy
     */
    public void setDataSource(@Nullable DataSource dataSource) {
        if (dataSource instanceof TransactionAwareDataSourceProxy) {
            // If we got a TransactionAwareDataSourceProxy, we need to perform transactions
            // for its underlying target DataSource, else data access code won't see
            // properly exposed transactions (i.e. transactions for the target DataSource).
            this.dataSource = ((TransactionAwareDataSourceProxy) dataSource).getTargetDataSource();
        } else {
            this.dataSource = dataSource;
        }
    }

    /**
     * Return the JDBC {@code DataSource} that this instance manages transactions for.
     */
    @Nullable
    public DataSource getDataSource() {
        return this.dataSource;
    }

    /**
     * Obtain the {@code DataSource} for actual use.
     *
     * @return the DataSource (never {@code null})
     * @throws IllegalStateException in case of no DataSource set
     * @since 5.0
     */
    protected DataSource obtainDataSource() {
        DataSource dataSource = getDataSource();
        Assert.state(dataSource != null, "No DataSource set");
        return dataSource;
    }

    /**
     * Specify whether to enforce the read-only nature of a transaction
     * (as indicated by {@link TransactionDefinition#isReadOnly()})
     * through an explicit statement on the transactional connection:
     * "SET TRANSACTION READ ONLY" as understood by Oracle, MySQL and Postgres.
     * <p>The exact treatment, including any SQL statement executed on the connection,
     * can be customized through {@link #prepareTransactionalConnection}.
     * <p>This mode of read-only handling goes beyond the {@link Connection#setReadOnly}
     * hint that Spring applies by default. In contrast to that standard JDBC hint,
     * "SET TRANSACTION READ ONLY" enforces an isolation-level-like connection mode
     * where data manipulation statements are strictly disallowed. Also, on Oracle,
     * this read-only mode provides read consistency for the entire transaction.
     * <p>Note that older Oracle JDBC drivers (9i, 10g) used to enforce this read-only
     * mode even for {@code Connection.setReadOnly(true}. However, with recent drivers,
     * this strong enforcement needs to be applied explicitly, e.g. through this flag.
     *
     * @see #prepareTransactionalConnection
     * @since 4.3.7
     */
    public void setEnforceReadOnly(boolean enforceReadOnly) {
        this.enforceReadOnly = enforceReadOnly;
    }

    /**
     * Return whether to enforce the read-only nature of a transaction
     * through an explicit statement on the transactional connection.
     *
     * @see #setEnforceReadOnly
     * @since 4.3.7
     */
    public boolean isEnforceReadOnly() {
        return this.enforceReadOnly;
    }

    @Override
    public void afterPropertiesSet() {
        if (getDataSource() == null) {
            throw new IllegalArgumentException("Property 'dataSource' is required");
        }
    }


    @Override
    public Object getResourceFactory() {
        return obtainDataSource();
    }

    @Override
    protected Object doGetTransaction() {
        DataSourceTransactionObject txObject = new DataSourceTransactionObject();
        txObject.setSavepointAllowed(isNestedTransactionAllowed());
        ConnectionHolder conHolder =
                (ConnectionHolder) TransactionSynchronizationManager.getResource(obtainDataSource());
        txObject.setConnectionHolder(conHolder, false);
        return txObject;
    }

    @Override
    protected boolean isExistingTransaction(Object transaction) {
        DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
        return (txObject.hasConnectionHolder() && txObject.getConnectionHolder().isTransactionActive());
    }

    @Override
    protected void doBegin(Object transaction, TransactionDefinition definition) {
        DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
        Connection con = null;

        try {
            if (!txObject.hasConnectionHolder() ||
                    txObject.getConnectionHolder().isSynchronizedWithTransaction()) {
                Connection newCon = obtainDataSource().getConnection();
                if (logger.isDebugEnabled()) {
                    logger.debug("Acquired Connection [" + newCon + "] for JDBC transaction");
                }
                txObject.setConnectionHolder(new ConnectionHolder(newCon), true);
            }

            txObject.getConnectionHolder().setSynchronizedWithTransaction(true);
            con = txObject.getConnectionHolder().getConnection();

            Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
            txObject.setPreviousIsolationLevel(previousIsolationLevel);
            txObject.setReadOnly(definition.isReadOnly());

            // Switch to manual commit if necessary. This is very expensive in some JDBC drivers,
            // so we don't want to do it unnecessarily (for example if we've explicitly
            // configured the connection pool to set it already).
            if (con.getAutoCommit()) {
                txObject.setMustRestoreAutoCommit(true);
                if (logger.isDebugEnabled()) {
                    logger.debug("Switching JDBC Connection [" + con + "] to manual commit");
                }
                con.setAutoCommit(false);
            }

            prepareTransactionalConnection(con, definition);
            txObject.getConnectionHolder().setTransactionActive(true);

            int timeout = determineTimeout(definition);
            if (timeout != TransactionDefinition.TIMEOUT_DEFAULT) {
                txObject.getConnectionHolder().setTimeoutInSeconds(timeout);
            }

            // Bind the connection holder to the thread.
            if (txObject.isNewConnectionHolder()) {
                TransactionSynchronizationManager.bindResource(obtainDataSource(), txObject.getConnectionHolder());
            }
        } catch (Throwable ex) {
            if (txObject.isNewConnectionHolder()) {
                DataSourceUtils.releaseConnection(con, obtainDataSource());
                txObject.setConnectionHolder(null, false);
            }
            throw new CannotCreateTransactionException("Could not open JDBC Connection for transaction", ex);
        }
    }

    @Override
    protected Object doSuspend(Object transaction) {
        DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
        txObject.setConnectionHolder(null);
        return TransactionSynchronizationManager.unbindResource(obtainDataSource());
    }

    @Override
    protected void doResume(@Nullable Object transaction, Object suspendedResources) {
        TransactionSynchronizationManager.bindResource(obtainDataSource(), suspendedResources);
    }

    @Override
    protected void doCommit(DefaultTransactionStatus status) {
        DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
        Connection con = txObject.getConnectionHolder().getConnection();
        if (status.isDebug()) {
            logger.debug("Committing JDBC transaction on Connection [" + con + "]");
        }
        try {
            con.commit();
        } catch (SQLException ex) {
            throw translateException("JDBC commit", ex);
        }
    }

    @Override
    protected void doRollback(DefaultTransactionStatus status) {
        DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
        Connection con = txObject.getConnectionHolder().getConnection();
        if (status.isDebug()) {
            logger.debug("Rolling back JDBC transaction on Connection [" + con + "]");
        }
        try {
            con.rollback();
        } catch (SQLException ex) {
            throw translateException("JDBC rollback", ex);
        }
    }

    @Override
    protected void doSetRollbackOnly(DefaultTransactionStatus status) {
        DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
        if (status.isDebug()) {
            logger.debug("Setting JDBC transaction [" + txObject.getConnectionHolder().getConnection() +
                    "] rollback-only");
        }
        txObject.setRollbackOnly();
    }

    @Override
    protected void doCleanupAfterCompletion(Object transaction) {
        DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;

        // Remove the connection holder from the thread, if exposed.
        if (txObject.isNewConnectionHolder()) {
            TransactionSynchronizationManager.unbindResource(obtainDataSource());
        }

        // Reset connection.
        Connection con = txObject.getConnectionHolder().getConnection();
        try {
            if (txObject.isMustRestoreAutoCommit()) {
                con.setAutoCommit(true);
            }
            DataSourceUtils.resetConnectionAfterTransaction(
                    con, txObject.getPreviousIsolationLevel(), txObject.isReadOnly());
        } catch (Throwable ex) {
            logger.debug("Could not reset JDBC Connection after transaction", ex);
        }

        if (txObject.isNewConnectionHolder()) {
            if (logger.isDebugEnabled()) {
                logger.debug("Releasing JDBC Connection [" + con + "] after transaction");
            }
            DataSourceUtils.releaseConnection(con, this.dataSource);
        }

        txObject.getConnectionHolder().clear();
    }


    /**
     * Prepare the transactional {@code Connection} right after transaction begin.
     * <p>The default implementation executes a "SET TRANSACTION READ ONLY" statement
     * if the {@link #setEnforceReadOnly "enforceReadOnly"} flag is set to {@code true}
     * and the transaction definition indicates a read-only transaction.
     * <p>The "SET TRANSACTION READ ONLY" is understood by Oracle, MySQL and Postgres
     * and may work with other databases as well. If you'd like to adapt this treatment,
     * override this method accordingly.
     *
     * @param con        the transactional JDBC Connection
     * @param definition the current transaction definition
     * @throws SQLException if thrown by JDBC API
     * @see #setEnforceReadOnly
     * @since 4.3.7
     */
    protected void prepareTransactionalConnection(Connection con, TransactionDefinition definition)
            throws SQLException {

        if (isEnforceReadOnly() && definition.isReadOnly()) {
            try (Statement stmt = con.createStatement()) {
                stmt.executeUpdate("SET TRANSACTION READ ONLY");
            }
        }
    }

    /**
     * Translate the given JDBC commit/rollback exception to a common Spring
     * exception to propagate from the {@link #commit}/{@link #rollback} call.
     * <p>The default implementation throws a {@link TransactionSystemException}.
     * Subclasses may specifically identify concurrency failures etc.
     *
     * @param task the task description (commit or rollback)
     * @param ex   the SQLException thrown from commit/rollback
     * @return the translated exception to throw, either a
     * {@link org.springframework.dao.DataAccessException} or a
     * {@link org.springframework.transaction.TransactionException}
     * @since 5.3
     */
    protected RuntimeException translateException(String task, SQLException ex) {
        return new TransactionSystemException(task + " failed", ex);
    }


    /**
     * DataSource transaction object, representing a ConnectionHolder.
     * Used as transaction object by DataSourceTransactionManager.
     */
    private static class DataSourceTransactionObject extends JdbcTransactionObjectSupport {

        private boolean newConnectionHolder;

        private boolean mustRestoreAutoCommit;

        public void setConnectionHolder(@Nullable ConnectionHolder connectionHolder, boolean newConnectionHolder) {
            super.setConnectionHolder(connectionHolder);
            this.newConnectionHolder = newConnectionHolder;
        }

        public boolean isNewConnectionHolder() {
            return this.newConnectionHolder;
        }

        public void setMustRestoreAutoCommit(boolean mustRestoreAutoCommit) {
            this.mustRestoreAutoCommit = mustRestoreAutoCommit;
        }

        public boolean isMustRestoreAutoCommit() {
            return this.mustRestoreAutoCommit;
        }

        public void setRollbackOnly() {
            getConnectionHolder().setRollbackOnly();
        }

        @Override
        public boolean isRollbackOnly() {
            return getConnectionHolder().isRollbackOnly();
        }

        @Override
        public void flush() {
            if (TransactionSynchronizationManager.isSynchronizationActive()) {
                TransactionSynchronizationUtils.triggerFlush();
            }
        }
    }
}
